Prep Glass: Fill an Old Fashioned or Rocks glass with ice. Give it a quick stir and set it aside.
Muddle Berries: Drop 4 fresh raspberries and 2 fresh blackberries into the shaker. Muddle well to release their juice.
Add Crème de Cassis: Add ¼ oz Creme de Cassis.
Add Drambuie: Measure and add ¾ oz Drambuie.
Add Irish Whiskey: Finally, add 2 oz Irish Whiskey to the mix.
Add Mint: Drop approx. 8-12 fresh mint leaves into the shaker as well.
Shake Well: Fill the shaker with ice, close it, and give it a good shake (10-15 seconds).
Strain: Discard the ice in the Old Fashioned glass and refill it with a generous amount of fresh, new ice cubes. Then, using both the cocktail strainer and fine strainer, strain the drink into the ice-filled glass.
Garnish: Garnish with a mint sprig and a few extra berries (you can either place them directly into the glass or use a cocktail skewer to hold them together). Serve immediately.